Biochar preparation from Parthenium hysterophorus and its potential use in soil application

Besides soil carbon sequestration, thermal conversion of weeds like Parthenium hysterophorus to biochar would be a sustainable weed management strategy. Parthenium was charred at different temperature (200–500 °C) and residence time (30–120 min). With increase in temperature, biochar yield decreased, whereas the stability increased. Stable organic matter yield index (SOMYI) was higher at 300–350 °C temperate with 30–45 min residential time. Elemental analysis, TGA, and FTIR, indicated the aromaticity and stability of biochar carbon. GC–MS spectra showed that ambrosin, an allelochemical present in Parthenium was lost during pyrolysis. Laboratory experiments on effect of Parthenium biochar (PBC) on soil microbial activity and Zea mays showed an increase in seedling vigour index with PBC addition. Soil dehydrogenase activity (DHA) increased (P < 0.05) from 5 g/kg PBC onwards; catalase activity increased at lower doses (1 and 3 g/kg PBC). Hydrolytic enzyme activities decreased with PBC application. Active microbial biomass carbon was 1.4, 1.7, and 2.1 times higher than control at 1, 3, and 5 g/kg PBC treatments, respectively. Basal soil respiration progressively increased up to 20 g/kg PBC. The stress indicator or the metabolic quotient decreased with PBC application and no adverse effect was observed even at the highest rate of PBC addition.

► Conversion of Parthenium residues to biochar is a new weed management strategy.
► Carbonization at 300–350 °C for 30–45 min yielded the desired biochar.
► Elemental analysis, TGA, and FTIR, indicated the aromaticity of biochar carbon.
► Allelochemical, ambrosin present in Parthenium residue was not detected in biochar.
► Maize seedling growth and soil biological activity enhanced due to biochar addition.